Gravity
From MB Wiki
Our elevation correction available to all customers.
Check out our blog post (http://clarque.typepad.com/mblog/2005/05/mb_gravity_elev.html) until we can get more time to write up the goods.
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How it Works
MB Gravity is a web service that cross references the horizontal position (latitude/longitude) provided by the GPS with an elevation that has been acquired by professional survey. When MB Gravity is applied, each trackpoint of your track now contains the elevation from the Gravity web service, not the elevation provided by your GPS device.
Assigning MB Gravity
MB Gravity is not applied to an activity by default. It may be applied:
Manually
Go to the Activity Options for the activity of interest. Check the Auto-Correct and MB Gravity options and submit.
Automatically
Set up your Account Preferences to automatically apply Auto-Correct and Gravity when you submit an activity from your Inbox to your Digest.
Recommended
Gravity is recommended for people using GPS units without barometric altimeters. For people with the Edge 305 Gravity is Not Recommended since the elevation on the device is more accurate.
Known Limitations
Steep Terrain
In areas with that are rather steep, MB Gravity will tend to report too much elevation change. We are looking into improving the corrections to reflect a more realistic cumulative elevation. The details about why this is having problems is complex and proprietary information at this moment, but know that we will do our best to correct this problem.
International Boundaries
Gravity will do its best to switch between datasets of International boundaries (mostly Canada and US), however, sometimes activities that cross over often will show uneven transitions.
Water
Lakes and oceans seem to effect elevation data for areas outside the US. This is most likely due to the technology used to record the elevation. Similar effects can be observed in Google Earth.
Bridges
Crossing bridges and other man-made structures will most likely report an elevation lower than actual. The elevation data represents the ground elevation and not the elevation of the bridge.
Worldwide Support
MB Gravity is now working worldwide! Play around with it as the resolution may not be as good in some areas.
High Resolution
The following countries will show better results with Gravity.
- United States
- Canada
Unsupported
Any land (independent of political boundaries) that is too far north or south (approx greater than 60 degrees latitude).
